The car is only 3 months old and I don't even drive it in the rain. Is there anything I can use to get rid of the rust and to stop it coming back ? Also I noticed that the driveshaft is pretty rusty too.

hammerite the driveshaft, the discs will always rust due to the iron content, doesn't matter if you drive in the rain or not. some pant that part but i wouldn't bother personally because a) when the wheels are on you can't even see it and b) unless the layer of paint is absolutely flat it may causes wheel vibration similar to what you'd get with inbalanced wheels

If I look at your gearbox, either the car was stored in a salty atmosphere, or you live near the sea.
Your disc's will always corrode, but I would clean the flanges and put some silicone grease on the contact surfaces, to avoid your alloy to corroded to your alloy.
You could paint the drive shaft if you want, it will never rust through, but it will look better for it.

I had the same prob and my car at the time was only 2 months old build in the spring and not even seen winter and they was like yours when I removed the wheels to seal

I contacted built hamber and bare in mind built hamber only used to do anti rust stuff way befor car waxes etc so they know what they are talking about

They told me to clean them up I used a dremel with a wire brush so I could get in the small bits
Then coat the bare metal (that is if you don't want to paint them) with
Built hamber DYNAX-UK wax
It's a see through clear wax and it's working good so far and seems fine but the next few months will be a real test